It is a curious experience to be both outplayed and wronged. A wry Celtic supporter struck the correct balance in a well-constructed complaint. "They weren't the ones needing help from the officials," he said in mock indignation. The Dimitar Berbatov goals that put Manchester United 2-0 ahead had been taken from marginally offside positions.

There could be no tirade from the Celtic manager, Gordon Strachan, even if he did touch upon the lapses by the referee, Frank de Bleeckere, and his assistants. Eventually United's superiority was marked.

Injuries that ruled out the strikers Jan Vennegoor of Hesselink and Georgios Samaras went part of the way to explaining the visitors' ineffectuality but the deeper truth lies in the divided nature of the Champions League. United and Villarreal are already close to qualification for the group phase, while Celtic and Aalborg grapple for a spot in the Uefa Cup.

Swift progress is virtually demanded at English clubs by managers who know that energy has to be conserved for the Premier League. There could be no element of the unknown in this meeting of title-holders from either side of the border. All the same the élan from Sir Alex Ferguson's team was fitful.

It mattered little that a groin injury kept Rio Ferdinand out. The line-up for the Champions League holders looked designed to deal briskly with Celtic but Strachan's side were competitive at the outset. United, however, can be patient, as they showed at the weekend when their four goals against West Bromwich Albion all came in the second half. Indeed a Darren Fletcher goal against Newcastle in August remains the only one scored here in the first half of any league fixture.

When Celtic did fall behind, in the 30th minute, the goal was galling. John O'Shea got a foot to Nani's corner but Berbatov was fractionally offside as he put the ball into the net. A team with the away record in the Champions League of Celtic is under enough pressure as it is without errors from officials.

They have now drawn one and lost the other 18 fixtures on their travels in this competition. With his team's two tall forwards ruled out, Strachan had mused about the possibility of Snow White leading out the side. The line-up was not uniformly diminutive but the manager was wise to look for relaxing humour.

Celtic gave a reasonable account of themselves before the interval. At that stage United had been flat. Only the composition of the team suggested verve, with Cristiano Ronaldo and Nani flanking the central strikers, Wayne Rooney and Berbatov. Strachan's team were containing that attack and, before half-time, had carried some menace of their own.

It was Edwin van der Sar who needed to make saves, putting efforts by Aiden McGeady and Gary Caldwell behind. Celtic's system of containment was functioning, yet United are well accustomed to wrecking plans of that sort.

The danger to Celtic was sporadic. Nani set up Rooney for a drive that was blocked by Mark Wilson and later Ronaldo missed the target from a promising position. All the same Fletcher, on the verge of the interval, should have doubled the lead instead of hacking Rooney's chip over the bar. Celtic had performed better than many had imagined, yet were losing and at risk of more harm.

Six minutes into the second half United killed off this match. Though Ronaldo's free-kick moved in the air, the goalkeeper Artur Boruc ought to have done better than palm it into the middle of the goalmouth, from where Berbatov scored a second time. The Bulgarian had again been marginally offside when the set piece was taken but soon afterwards the flag was raised wrongly against Rooney when he had the ball in the net. It is a moot point whether Celtic's mood will be improved by evidence that poor officiating was at work rather than a conspiracy.

Berbatov is most likely cursing machinations but there was nothing covert about them. The forward was denied the prospect of a hat-trick because Ferguson replaced him with Carlos Tevez. Having made sure of the win here, the manager attended to forward planning. The player removed will have to content himself with a spree of five goals in four matches.

There was no more than professionalism to sustain the visitors. Tevez was soon compelling Boruc to tip an attempt round the post. Rooney made the goalkeeper put a shot over the bar before striking at last in the 76th minute, from a Tevez pass. This had been one more away match in Europe to be met with stoicism by Celtic.